Sens. Lindsey Graham, Bill Cassidy, Dean Heller and Ron Johnson on Wednesday released an Obamacare repeal bill, framing it as the last, best hope to fulfill the GOP’s promise to undo the health law.

“There’s a lot of fight left in the Republican Party” on repeal, Graham said.

The bill faces long odds: Even some of its GOP backers say it would be almost impossible to get a massive rewrite of the health care system through the Senate within 17 days, or before the expiration of fast-track procedural powers Republicans hope to use to bypass the threat of a Democratic filibuster.

President Donald Trump praised the lawmakers for continuing to work on Obamacare repeal, citing the “complete nightmare” the law is for Americans. But he didn’t indicate whether he would press lawmakers to support the measure. “I sincerely hope that Senators Graham and Cassidy have found a way to address the Obamacare crisis,” he said in a statement.

Graham called on Trump, Vice President Mike Pence and Senate GOP leaders to help them gather 50 votes. Majority Leader Mitch McConnell, who brought up several repeal measures in July only to see all of them fail, has said he’d bring up any Obamacare repeal bill that has enough Republican support. McConnell on Tuesday refused to choose between the repeal bill or a bipartisan measure being drafted by GOP Sen. Lamar Alexander and Democratic Sen. Patty Murray.

Graham said Trump, Pence and McConnell should put all of their effort into lobbying Republican lawmakers to back the bill.

“The idea that the Republican Party has done its best to repeal and replace Obamacare is a joke,” the South Carolina Republican said.

The $1.2 trillion bill, H.R. 1628 (115), which has been at the CBO for about one week, according to the senators, would provide states with block grants instead of Obamacare’s tax credits, Medicaid expansion and cost-sharing payments. It would also repeal Obamacare’s individual and employer mandates and the medical device tax.

In general, Republicans favor giving the states a “block grant” of funding to create their own health care systems. The repeal bill attempts to equalize health care spending by the federal government to states.

Some states, particularly high-cost places such as Massachusetts, are bound to be worse off under the measure than less expensive parts of the country.

It’s unclear if the CBO would even have time to score the bill before the end of the month. It would also have to go before the Senate parliamentarian to ensure that it complies with the rules of the expedited procedure, called reconciliation.

In addition, some conservatives have been cool to the legislation because it keeps many Obamacare taxes and doesn’t do enough to undo the law. The message from the bill’s authors on Wednesday was that they had to do something.

“This is our last shot,” Johnson said. “I will never let perfect be the enemy of good. … This is far better than Obamacare.”

Johnson said he would hold a hearing on the plan by Sept. 30 in the Senate Homeland Security and Governmental Affairs Committee that he leads if the HELP and Finance committees that share jurisdiction over health issues don’t.